Home network system with transmission error recovery

ABSTRACT

A client TV in a home entertainment network receives and buffers an audio/video stream from a server, before playing the stream. In the case of buffer underflow, the client TV requests the server to raise the transmission rate. If this causes an ensuing buffer overflow, the client TV requests the server to reset the transmission rate or stop transmitting altogether for a short time.

RELATED APPLICATIONS

This application claims priority from U.S. provisional patentapplication Ser. No. 60/591,455, filed Jul. 27, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to home entertainment systems.

2. Description of the Related Art

Home entertainment systems have been provided that can include a set-topbox media server that communicates with various components in the home,e.g., TVs, laptop computers, and custom display devices. Home networkcommunication technologies (e.g., 802.11 wireless, UWB (Ultra WideBand), PLC (Power Line Communication), etc.) are widely used as theircosts decrease.

As critically recognized herein, wireless home networks are not asreliable as wired and dedicated networks such as Ethernet. Consequently,audio/video data packets frequently can be lost (“dropped”) intransmission. When a transmission is not time critical, retransmissionof a dropped packet is not a problem. An example of such a non-timecritical transmission is a file transfer that can be performed usingTransmission Control Protocol/Internet Protocol (TCP/IP), which includesa retransmission mechanism.

However, for time critical audio/video (A/V) streaming, retransmissioncan be problematic. Usually, a client, such as a TV, has a limitedamount of buffer to decode the A/V stream and pass the decoded data onfor playing. Retransmission takes time, and this can cause underflow ofthe client buffer, meaning that the buffer can empty itself of databefore dropped packets are received pursuant to retransmission. Also, anopposite problem can occur at the home network system server, namely,during retransmission, new data can arrive from the outside source(cable, antenna, etc.) and the server's transmission data bufferoverflows, because the server holds the new data in its buffer until thedropped packet is received by the client. As understood herein, thisproblem can be serious particularly in the case of live streaming,because the stream rate is not controllable at all. As furtherrecognized herein, the above-mentioned problems of buffer underflow andoverflow can cause visible video errors or audible noise, diminishingthe quality of the A/V display and, thus, the viewer's enjoyment.

SUMMARY OF THE INVENTION

A home entertainment system includes a server and at least one clientcomponent communicating with the server on a network path. The clientcomponent buffers data received from the server and monitors the amountof buffered data. If it is determined that the amount of buffered datafalls below an underflow threshold, the client component sends a requestto the server to raise the rate at which data is transmitted. If it isdetermined that the amount of buffered data exceeds an overflowthreshold subsequent to raising the rate at which data is transmitted,the client component requests the server to reset the transmission rateback to an original rate, or it requests the server to stop transmissionaltogether.

In some implementations an MPEG transcoder in the server is used forautomatic bit rate control of data transmitted to the client component.Under unfavorable network conditions the transcoder can transcode a datastream to a lower bit rate stream and send the lower bit rate streamfaster than a normal operating data transfer rate. The server mayreceive the data from a source of live audio/video data and may bufferthe data before sending the data to the client component. Or, a livestream can be recorded by the client component in a buffer, with theamount of buffered data being controlled between two thresholds duringplaying of the data to avoid over/underflow. The client component may beselected from the group of components consisting of: televisions, andportable computers.

In another aspect, a method is disclosed for playing an audio/videostream on a client TV communicating with a server in a homeentertainment network. The method includes transmitting the stream fromthe server to the client TV, and while transmitting, buffering thestream at the client TV. The method also includes playing the stream atthe client TV, monitoring an amount of buffered data during the playingact, and, in the event that the amount of buffered data falls below anunderflow threshold, increasing the rate at which the stream istransmitted from the server to the client TV.

In still another aspect, a TV that is configured for use in a homeentertainment network including a server and a network communicationpath includes means for monitoring a data buffer and means for comparingan amount of data in the buffer to an underflow threshold. Means areprovided for causing the server to increase the rate at which data istransmitted to the TV over the network if the amount of data in thebuffer falls below the underflow threshold. Also, means are provided forcausing the server to undertake at least one of: decreasing the rate atwhich data is transmitted to the TV over the network, and temporarilystopping transmission to the TV, if the amount of data in the bufferrises above an overflow threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

The details of the present invention, both as to its structure andoperation, can best be understood in reference to the accompanyingdrawings, in which like reference numerals refer to like parts, and inwhich:

FIG. 1 is a block diagram of a network according to the presentinvention;

FIG. 2 is a block diagram of the server of the present invention;

FIG. 3 is a block diagram of a client TV;

FIG. 4 is a flow chart of the present logic.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the preferred non-limiting embodiment shown, the processors describedherein may access one or more software or hardware elements to undertakethe present logic. The flow charts herein illustrate the structure ofthe logic modules of the present invention as embodied in computerprogram software, in logic flow chart format, it being understood thatthe logic could also be represented using a state diagram or otherconvention. Those skilled in the art will appreciate that the flowcharts illustrate the structures of logic elements, such as computerprogram code elements or electronic logic circuits, that functionaccording to this invention. Manifestly, the invention is practiced inits essential embodiment by a machine component that renders the logicelements in a form that instructs a digital processing apparatus (thatis, a computer or microprocessor) to perform a sequence of functionsteps corresponding to those shown. Internal logic could be as simple asa state machine.

In other words, the present logic may be established as a computerprogram that is executed by a processor within, e.g., the presentmicroprocessors/servers as a series of computer-executable instructions.In addition to residing on hard disk drives, these instructions mayreside, for example, in RAM of the appropriate computer, or theinstructions may be stored on magnetic tape, electronic read-onlymemory, or other appropriate data storage device.

Referring initially to FIG. 1, a system is shown, generally designated10, which shows an example of a power line network and connecteddevices. As shown, a home network server 12 can receive an A/V signalfrom a cable signal receiver 14 or it can receive Internet data, e.g.,streaming video, from a computer modem 16. The modem 16 can be, forexample, a cable modem or an Asymmetric Digital Subscriber Line (ADSL)modem. In turn, the server 12 sends received audio/video streams to aclient player, such as but not limited to a client TV 18, over a powerline 20, it being understood that communication between the client andserver can also be wireless or can alternatively be wireless. That is,the present invention applies to various types of home networksincluding those that use Wireless Fidelity (802.11b) (WiFi), HomePhoneline Networking Alliance (HPNA), coaxial cable, Ethernet, and soon.

The client TV 18 decodes the stream and displays decoded video on itsscreen. If desired, the client TV 18 can wirelessly receive commandssuch as play, stop, channel up/down, volume up/down from a remotecommander 22. Some of these commands, for example, a channel up/downcommand, can be forwarded to the server 12.

FIG. 2 shows a block diagram of the server 12. Analog cable signals aretuned and demodulated in an analog tuner front end 24. The video outputfrom the analog tuner front end 24 is then digitized by a video analogto digital converter 26 and encoded in Motion Picture Engineering Group(MPEG) format in an MPEG encoder 28. Similarly, the audio output fromthe analog tuner front end 24 is digitized by an audio ADC 30 andMPEG-encoded by the MPEG encoder 28. The A/V stream that is output bythe MPEG encoder 28 is then sent to a stream router 32.

In the case of digital cable signals, the digital cable signals can bereceived for tuning and demodulating at a digital tuner front end 34.The signal that is output by the digital front end 34, which may beencrypted for content protection, can be decrypted in a ConditionalAccess Module (CAM) interface 36, which can decrypt the stream incooperation with an access card 38 in accordance with decryptionprinciples known in the art. The decrypted stream is then sent to thestream router 32.

In accordance with home network routing principles, the stream router 32routes, i.e., establishes the output direction, for each incomingstream. Also, the stream router 32 can multiplex plural streams into oneoutput stream if necessary.

Specifically, the stream router 32 can send an incoming stream from theMPEG encoder 28 directly to a power line communication (PLC) interface40. In contrast, an incoming decrypted digital cable stream from the CAMinterface 36 can be sent to the PLC interface directly or it can be sentto the PLC interface 40 via an MPEG transcoder 42, which transcodes theincoming stream at a lower rate than the original stream in accordancewith further disclosure below. In contrast, streams from the MPEGencoder 28 do not need separate transcoding because the MPEG encoder 28can be used to directly adjust the bit rate of the stream in accordancewith present principles set forth below.

In a recording mode, the incoming stream from the MPEG encoder 28 orfrom the CAM interface 36 is sent to a storage, such as a hard diskdrive (HDD) 44 with attendant HDD interface 46, which appends atimestamp to each packet in the stream to record. The incoming streamfrom the CAM interface 36 may be transcoded by the MPEG transcoder 42before being sent to the HDD 44 for conserving HDD storage space.

Accordingly, when playing back recorded content, a playback stream fromthe server HDD 44 is sent to the stream router 32 through the HDDinterface 46, which injects each packet into the transmitted data basedon its timestamp. The stream router 32 can send the stream to the PLCinterface 40 directly or via the MPEG transcoder 42 for bit ratereduction in accordance with principles set forth further below, fortransmission to the client TV 18 and playing thereon.

Still referring to FIG. 2, the server 12 includes a central processingunit (CPU) 48 that controls the server 12 components through an internaldata bus 50, to which the components are connected. Thus, the CPU 48executes control software, described below, that can be stored in asolid state server memory 52. Also, an input device such as a keypad 54can be used to input data to the CPU 48 through the bus 50, while anoutput device such as a liquid crystal display (LCD) 56 can be used toindicate various data from CPU 48, e.g., tuning status, network status,error messages, etc. The modem 16 shown in FIG. 1 can be connected to anEthernet port 58 so that data from the modem 16 can be sent to the CPU48 through an Ethernet interface 60 for processing.

Now referring to FIG. 3, a block diagram of the client TV 18 is shown. APLC Interface 62 can receive signals sent from the server 12 over thepower line 20. The output signal from the PLC interface 62 isdemultiplexed in a demultiplexer 64, with the audio portion being sentto an audio decoder 66 and with the video portion being sent to a videodecoder 68. A mixer 70 receives the video portion and can mix the videowith graphics data generated in by a graphics engine 72 if desired. Thevideo is then converted to analog by a video digital to analog converter74 and sent to a display driver 76, for presentation on a display 78.The display 78 may be a cathode ray tube display or flat panel displayor other TV display, and may user either or both standard video formatand high definition TV format.

With respect to the analog portion of the stream, once decoded, theaudio is analogized at an audio digital to analog converter 80 andamplified by an amplifier 82. The signal is then sent to speakers 84, itbeing understood that the audio circuitry set forth above canaccommodate two or more audio channels as indicated by the “slash 2”symbols in FIG. 3.

The TV 18 can be placed in a recording mode, wherein the demultiplexer64 sends the incoming stream from the PLC interface 62 to a HDDinterface 86. The stream is recorded onto a TV HDD 88. Accordingly, aplayback stream may be sent from the HDD 88 to the demultiplexer 64through the HDD interface 86, with the demultiplexer 64 sending thestream to the audio decoder 66 and video decoder 68 for processing asdescribed above.

As shown in FIG. 3, the TV 18 can include a CPU 90 that exchangesasynchronous data (commands, data, etc.) with the server CPU shown inFIG. 2 over the power line 20. As shown, the CPU 90 can control the PLCinterface 62 and demultiplexer 64 through an internal TV data bus 92.Also, the CPU 90 executes logic in accordance with principles set forthherein that may be stored in a TV solid state memory 94. Furthermore, awireless interface 96 can receive commands from the remote commander 22,e.g., using infrared or radio frequency communication principles knownin the art, with the wireless interface 96 being connected to theinternal TV data bus 92 for communication with the TV CPU 90.

When an A/V stream that is stored in the server HDD 44 is to be copiedto the client TV HDD 88, as recognized herein if a packet drop occursduring transmission, the transmission simply stops and the lost packetis retransmitted without further considerations, since the transfer isnot a time critical operation. On the other hand, the present inventionunderstands that retransmission complications can arise in the casewherein an A/V stream that is stored in the server HDD 44 is to beplayed on the client TV 18.

More particularly and now referring to FIG. 4, as understood herein theclient TV 18 temporarily stores some amount of the stream data, forexample data associated with thirty seconds of play, in its HDD 88 forbuffering, and then starts A/V decoding. The client TV demultiplexer 64injects a packet to both the decoders 66 and 68 based on the timestampof the packet given by the client HDD interface 86 during buffering. Asunderstood herein, if isochronousness is not kept, the decoders 66 and68 can cause buffer overflow or underflow and consequently someaudio/video errors will occur.

Accordingly, at block 100 in FIG. 4 the client TV CPU 90 monitors theamount of buffering in the client TV HDD 88. If it is determined atdecision diamond 102 that the amount of buffered data falls below anunderflow threshold, the logic proceeds to block 104, wherein the clientTV 18 sends a request to the server 12 to raise the transmission rate.

From block 104 or from decision diamond 102 when the test there isnegative, the logic proceeds to decision diamond 106, wherein it isdetermined whether the amount of buffered data exceeds an overflowthreshold. If it does the logic proceeds to block 108 wherein the clientTV 18 requests the server 12 to reset the transmission rate back to theoriginal value. Alternatively, the client TV CPU 90 may request theserver 12 to stop transmission altogether, in which case transmissiondoes not restart until the amount of buffered data falls below the upperthreshold again. When the stream is sent at the faster rate than normal,all the timestamps can be ignored. From block 108 or from decisiondiamond 106 if the test there was negative, the logic loops back toblock 100.

It is to be understood that in alternate embodiments the server 12 canmonitor the content of the client TV buffer and automatically executethe logic above without waiting for requests from the client TV 18.

As mentioned above, the MPEG transcoder 42 in the server 12 can be usedfor automatic bit rate control in response to the requests from theclient TV discussed in reference to FIG. 4. In case of heavy traffic orunfavorable transmission conditions, the transcoder 42 can reduce thestream bit rate and prevent audio/video corruption at the client TV 18.However, no packet drop error can be saved with this mechanism.Accordingly, to resolve this, the transcoded stream can be sent at afaster rate. When powerline transmission conditions are not good or whenthe power line network 20 has heavy traffic or otherwise experiencesunfavorable conditions, however, the server 12 cannot send the stream ata faster rate, because doing so would require more bandwidth. In such acase, the MPEG transcoder 42 transcodes the stream into a lower ratestream, and all the timestamps should be ignored and the MPEG transcoder42 run faster than the normal speed.

For example, assume the original rate of the stream is 8 Mbit/sec andthat the stream is transcoded to a half rate, 4 Mbit/sec stream. If theMPEG transcoder 42 runs at the original rate, a valid packet will beoutput in every other packet slot. The bandwidth usage consequently ishalf that of the original stream, but the time required for transmittingthe data remains the same. When a packet drop necessitates aretransmission and, hence, causes some delay, the buffer in the ClientTV 18 could underflow. Therefore, as set forth above the MPEG transcoder42 runs faster, in which case the original bandwidth of 8 Mbit/sec ispreserved and the server 12 can send the stream roughly twice as fast,although in practice only 20% to 30% faster speed is sufficient forretransmission recovery.

The above principles can also be applied to recording a live stream fromthe antenna or cable end onto the client TV HDD 88, which live streamcannot be sent at a faster rate without buffering. The incoming streamis temporarily stored in the server HDD 44, and when the amount ofbuffered data exceeds a certain threshold, data transmission can startat a faster rate. When the amount of buffered data falls below thethreshold, the transmission stops, to avoid buffer underflow. If thebandwidth of the power line 20 is limited, transcoding may be performedas described above.

In this recording mode, the client TV 18 does not consider packettimestamps or buffer over/underflow. Instead, received data packetssimply are stored in the client TV HDD 88 one after another. When thestream is played, it is decoded based on the timestamps stored with thepackets.

When a live stream is decoded at the client TV 18, the transmissionmechanism is the same in live stream recording at the client TV 18. Onthe client side, received data is temporarily stored in the client HDD88 and decoded based on the timestamps. The amount of buffered data inthe client HDD 88 is controlled between the thresholds discussed abovein relation to FIG. 4 to avoid over/underflow.

In specific non-limiting implementations, each client in the system 10can have a predetermined buffer size. Although a HDD is used in theabove examples, a semiconductor memory such as DRAM can also be used. Tostore a one minute long, 20 Mbit/sec MPEG-HD stream, a capacity of 150Mbytes (1200 Mbits) is required, whereas for SD streams, less than halfthat amount is required, placing the required buffer size within thereach of solid state memory devices.

It is to be understood that the principles advanced herein can beapplied to audio-only data streams and to other time-criticaltransmissions, and can also be applied to any network protocol,including isochronous, IP, etc.

As recognized herein, the present invention provides the advantages ofrendering the server 12 capable of transmitting a stream to the clientat a faster rate than the original rate to save time for retransmission.The client 18 can buffer a certain amount of data and decode the stream,and when a packet drop error occurs during transmission, retransmissionis facilitated without audio/video corruption. In the case of a livestream, the server 12 temporarily stores data in its storage andtransmits it at a relatively fast rate to the client, so that the clientcan record or playback the live stream as it does a recorded stream and,hence, facilitate error-free retransmission of dropped packets. In thecase when the network is busy or under unfavorable conditions, theserver 12 cannot obtain more bandwidth to send the stream faster, inwhich case the stream is transcoded to a lower bit rate stream and sentfaster than the original rate without requiring additional networkbandwidth for retransmission.

While the particular HOME NETWORK SYSTEM WITH TRANSMISSION ERRORRECOVERY as herein shown and described in detail is fully capable ofattaining the above-described objects of the invention, it is to beunderstood that it is the presently preferred embodiment of the presentinvention and is thus representative of the subject matter which isbroadly contemplated by the present invention, that the scope of thepresent invention fully encompasses other embodiments which may becomeobvious to those skilled in the art, and that the scope of the presentinvention is accordingly to be limited by nothing other than theappended claims, in which reference to an element in the singular means“at least one”. All structural and functional equivalents to theelements of the above-described preferred embodiment that are known orlater come to be known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the present claims. Moreover, it is not necessary for adevice or method to address each and every problem sought to be solvedby the present invention, for it to be encompassed by the presentclaims. Furthermore, no element, component, or method step in thepresent disclosure is intended to be dedicated to the public regardlessof whether the element, component, or method step is explicitly recitedin the claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. section 112, sixth paragraph, unless the elementis expressly recited using the phrase “means for”.

I claim:
 1. A home entertainment system, comprising: at least oneserver; and at least one client component communicating with the serveron a network path, wherein the client component buffers data receivedfrom the server and monitors the amount of buffered data, wherein if itis determined that the amount of buffered data falls below an underflowthreshold, the client component sends a request to the server to raisethe rate at which data is transmitted, wherein a transcoder in theserver is used for automatic bit rate control of data transmitted to theclient component, and further wherein under unfavorable networkconditions the transcoder transcodes a data stream to a lower bit ratestream and sends the lower bit rate stream faster than a normaloperating data transfer rate.
 2. The system of claim 1, wherein if it isdetermined that the amount of buffered data exceeds an overflowthreshold subsequent to raising the rate at which data is transmitted,the client component undertakes at least one of: requesting the serverto reset the transmission rate back to an original rate, and requestingthe server to stop transmission altogether.
 3. The system of claim 1,wherein the server receives the data from a source of live audio/videodata and buffers the data before sending the data to the clientcomponent.
 4. The system of claim 1, wherein a live stream is recordedby the client component in a buffer, the amount of buffered data beingcontrolled between two thresholds during playing of the data to avoidover/underflow.
 5. The system of claim 1, wherein the client componentis selected from the group of components consisting of: televisions, andportable computers.
 6. The system of claim 5, wherein the clientcomponent is a TV.